1. Field Of The Invention
This invention relates to devices which can detect a small loss of refrigerant charge from refrigeration systems while in operation, and function to trigger an audible and/or visual alarm during any time the system is operating.
2. Description Of The Related Prior Art
The need for a method and apparatus to determine the amount of refrigerant in a refrigeration system, particularly a large system, has long been recognized. There are several reasons why this measurement is important, but the main concern for most refrigeration systems is the need to detect a low refrigerant condition as the result of a steady loss of refrigerant over time due to leaks in the pressurized system. A low refrigerant condition initially results in a gradual loss of cooling capacity which, if not detected and corrected, can result in such a critical loss of refrigerant that expensive damage can occur to a refrigerant compressor due to lubrication failure.
U.S. Pat. No. 4,553,400, issued Nov. 19, 1985 to Michael A. Branz, discloses a comprehensive refrigerant monitor and alarm system with emphasis on the electrical and electronic features of the system. When adapted to commercial refrigeration systems for supermarket display cases, it is seen that the level of refrigerant in a large common receiver is to be monitored by a conventional liquid level sensing float. A liquid level indicator provides a constant readout of the level in the receiver, triggers a timer controlled alarm when a critically low level is reached. By contrast, the present invention reliably detects a loss of refrigerant at a convenient, accessible location which can be located remotely from the receiver.
U.S. Pat. No. 4,308,725, issued Jan. 5, 1982 to Tsuneyuki Chiyoda discloses a simplistic device for detecting the quantity of refrigerant in a liquid receiver. In one embodiment, a floating hollow ball within a float guide can rise or fall with the refrigerant level, and as the level drops due to the loss of refrigerant, ultimately the ball comes in contact with a pair of electrical conducting elements, and the ball, being made of conductive material, then completes an alarm circuit through the contacts to energize an external alarm. An ingenious electronic circuit filters out very short electrical contact times in the detector which may be caused by mechanical vibrations. The positive make-or-break characteristics of the switching device of the present invention renders it largely immune to such rapid short contact times, as would be induced by mechanical vibration.
U.S. Pat. No. 4,745,765, issued May 24, 1988 to Edward D. Pettitt, discloses a refrigerant detecting device which illustrates a new inventive trend in liquid level sensors. This type of sensor responds to "condition sensing" and can determine a low refrigerant charge level without actually being located within or near a receiver containing the bulk of the liquid charge. This condition sensing device, located in the discharge line from an evaporator, detects refrigerant super heat temperature and also contains a bi-metal ambient air temperature sensor. An internal electrical contact closes to activate an alarm when a predetermined combination of evaporator super heat and ambient air temperature occurs indicating an undesirably low amount of refrigerant in the system. It is a complex precision device compared to the simplicity of the present invention.
U.S. Pat. No. 4,856,288, issued Aug. 15, 1989 to Robert C. Weber, discloses a refrigerant detection device which is to be installed at a predetermined location in a refrigerant high pressure liquid line. It consists of a preferably transparent hollow cylinder, a few inches in height in which a float of conductive material is disposed. As the conductive float follows the liquid level down in the cylinder, it eventually reaches a pair of electrically conductive contact points and thereby completes an electrical circuit which is indicative of refrigerant loss and therefore can activate a refrigerant low level alarm. Several embodiments of the invention are disclosed including versions having two conductive floats. A time delay means is suggested to avoid activation of the alarm during the compressor startup phase.
The conductive float sensor of this invention may be subject to short, rapid electrical contact times which can be caused by mechanical vibrations, same as referred to above for the Chiyoda Patent, but the present invention is immune to the effects of mechanical vibration and the resultant rapid contact cycling.
None of the above inventions and patents taken either singly or in combination, is seen to describe the instant invention as claimed.